Standard Number:<\/strong> GB\/T 6402-2008<\/p>\n Replaces:<\/strong> GB\/T 68402-1991<\/p>\n \u5df2\u51fa\u7248\uff1a<\/strong> 2008-05-13 Implemented:<\/strong> 2008-11-01<\/p>\n Issued by:<\/strong> General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China<\/p>\n Adopted from:<\/strong> EN 10228-3:1998 and EN 10228-4:1999<\/p>\n This standard specifies the agreement terms, procedural requirements, personnel qualification, equipment and accessories, calibration and verification, detection timing, surface conditions, sensitivity, scanning methods, classification, reporting levels, and acceptance criteria for ultrasonic testing of steel forgings.<\/p>\n This standard is applicable to manual ultrasonic pulse-echo testing of ferritic-martensitic steel forgings, austenitic and austenitic-ferritic duplex stainless steel forgings. Upon agreement between supplier and purchaser, mechanized scanning methods using immersion testing may also be employed. Forgings from other organizations may also refer to this standard.<\/p>\n Forgings are classified into 4 categories based on shape and production method. Categories 1, 2, and 3 are simple-shape forgings; Category 4 is for complex-shape forgings.<\/p>\n This standard does not apply to:<\/strong> dense die forgings, turbine rotors, and engine crankshafts.<\/p>\n The following referenced documents are indispensable for the application of this document:<\/p>\n Terms and definitions per GB\/T 12604.1 apply.<\/p>\n The following items should be agreed upon between supplier and purchaser before testing:<\/p>\n Ultrasonic testing shall be performed according to a procedure. When specified in the contract, the procedure shall be submitted to the purchaser for approval before testing. The procedure shall include at least the following:<\/p>\n Personnel qualification and certification shall be performed according to GB\/T 9445<\/strong> or applicable standards, and qualified certificates shall be obtained.<\/p>\n Equipment shall use A-scan display and comply with JB\/T 10061 requirements.<\/p>\n General:<\/strong> Straight-beam and angle-beam probes shall comply with GB\/T 18694. Probes with form-fitting shoes may be used when necessary to ensure good, uniform coupling and constant beam angle.<\/p>\n Nominal frequency range:<\/strong> 1.0 MHz – 6.0 MHz<\/p>\n Straight-beam probe:<\/strong> Effective crystal diameter 10 mm – 40 mm<\/p>\n Angle-beam probe:<\/strong> Refraction angle 35° – 70°; effective crystal area 20 mm² – 625 mm²<\/p>\n Dual-crystal probe:<\/strong> May be used if near-surface inspection is required<\/p>\n Shall comply with GB\/T 19799.1 requirements.<\/p>\n When sensitivity is set using the Distance-Amplitude Correction (DAC) method, a reference block shall be fabricated. Surface condition of the reference block should represent the surface condition of the tested forging. The reference block shall contain at least three reflectors covering the entire testing depth.<\/p>\n Acceptable couplants include water (with or without anti-rust agents or softeners), glycerin, oil, and water-soluble pastes. The same type of couplant shall be used for calibration, sensitivity setting, scanning, and discontinuity evaluation.<\/p>\n Equipment (flaw detector and probes) shall be calibrated and checked according to JB\/T 9214.<\/p>\n Ultrasonic testing shall be performed after final heat treatment<\/strong>, unless otherwise agreed at the time of order. For cylindrical and ring forgings about to be drilled, it is recommended to perform ultrasonic testing before drilling.<\/p>\n General:<\/strong> Scanning surfaces shall be free of paint, scale, dried couplant, or any substance that could cause coupling failure, hinder free probe movement, or cause false interpretations.<\/p>\n Surface roughness:<\/strong><\/p>\n Sensitivity shall be sufficient to detect the minimum discontinuity size required for the reporting level of the specified quality grade.<\/p>\n Either of the following methods may be used to determine scanning sensitivity:<\/p>\n DAC method using 3 mm diameter side-drilled holes.<\/p>\n If repeat testing is performed, the sensitivity determination method shall be the same as the original.<\/p>\n Manual contact scanning using pulse-echo method shall be used. The minimum scanning area depends on the forging category. Grid scanning vs. 100% scanning shall be specified in the contract.<\/p>\n For complex-shape forgings or complex sections, supplier and purchaser shall negotiate scanning requirements at the time of order, including: probe angle, scanning direction, scanning coverage (grid or 100%).<\/p>\n Grid scanning shall be performed using one or more probes moved along the grid lines specified in Tables 2 and 3. When a recordable indication is found, additional scanning around the indication shall be performed to determine its extent.<\/p>\n Adjacent probe movements shall overlap by at least 10% of the effective probe diameter.<\/p>\n Manual scanning speed shall not exceed 150 mm\/s<\/strong>.<\/p>\n Scanning coverage depends on forging category and dimensions. For 100% scanning, adjacent probe movements shall overlap by at least 10% of the effective probe diameter.<\/p>\n For Category 3 forgings: 360° circumferential grid scanning from two directions. Grid interval shall equal radial thickness, maximum 200 mm.<\/p>\n Based on dynamic echo patterns from scanning in at least two perpendicular directions:<\/p>\n The required quality grade shall be negotiated between supplier and purchaser. Four quality grades are defined, with Grade 4 being the strictest (smallest reporting level and acceptance criteria).<\/p>\n Reporting levels and acceptance criteria are based on equivalent flat-bottom hole diameter, specified by thickness range and quality grade (1 through 4). Grade 1: ≥Φ8mm reporting, <5mm acceptance for thickness ≤250mm. Grade 4: ≥Φ2mm reporting, bottom wave attenuation factor (Ff) criteria, complete bottom wave loss ≥5% of initial bottom echo.<\/p>\n Based on 3 mm diameter side-drilled holes. Recording levels and acceptance criteria specified by forging thickness and nominal frequency. For thickness ≤400 mm.<\/p>\n For linear discontinuity evaluation, one or more of the following methods shall be used (per JB\/T 4009):<\/p>\n The test report shall include the following information:<\/p>\n
\n1 Scope<\/h3>\n
2 Normative References<\/h3>\n
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3 Terms and Definitions<\/h3>\n
4 Agreement Items<\/h3>\n
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5 Procedure Preparation<\/h3>\n
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6 Personnel Qualification<\/h3>\n
7 Equipment and Accessories<\/h3>\n
7.1 Flaw Detector<\/h4>\n
7.2 Probes<\/h4>\n
7.3 Calibration Block<\/h4>\n
7.4 Reference Block<\/h4>\n
7.5 Couplant<\/h4>\n
8 Routine Calibration and Checks<\/h3>\n
9 Testing Timing<\/h3>\n
10 Surface Condition<\/h3>\n
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11 Sensitivity<\/h3>\n
11.1 General<\/h4>\n
11.2 Straight-Beam Probe<\/h4>\n
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11.3 Angle-Beam Probe<\/h4>\n
11.4 Repeat Testing<\/h4>\n
12 Scanning<\/h3>\n
12.1 General<\/h4>\n
12.2 Complex Forgings (Category 4)<\/h4>\n
12.3 Grid Scanning<\/h4>\n
12.4 100% Scanning Coverage<\/h4>\n
12.5 Scanning Speed<\/h4>\n
13 Classification<\/h3>\n
13.1 Forging Categories<\/h4>\n
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\n \u7c7b\u522b<\/th>\n Shape<\/th>\n Production Method<\/th>\n Examples<\/th>\n<\/tr>\n \n 1a<\/td>\n Circular or near-circular cross-section elongated parts<\/td>\n Forged, rolled, or drawn<\/td>\n Profiles, bars, columns, disks, shafts, necks<\/td>\n<\/tr>\n \n 1b<\/td>\n Square or near-square cross-section elongated parts<\/td>\n Forged, rolled, or drawn<\/td>\n Profiles, bars, blocks, large flat plates cut from ingots<\/td>\n<\/tr>\n \n 2<\/td>\n Flat, e.g., disks, plates<\/td>\n Forged or cut from plates<\/td>\n Flywheels<\/td>\n<\/tr>\n \n 3a<\/td>\n Hollow cylindrical<\/td>\n Forged, punched<\/td>\n Rings, pipe blanks, pressure vessel shells<\/td>\n<\/tr>\n \n 3b<\/td>\n Hollow cylindrical, thin rings\/disks<\/td>\n Forged, punched<\/td>\n Ring flanges, thin rings<\/td>\n<\/tr>\n \n 4<\/td>\n Complex-shape forgings or complex sections<\/td>\n Per manufacturer’s specification<\/td>\n Various complex parts<\/td>\n<\/tr>\n<\/table>\n 13.2 Straight-Beam Probe Scanning Coverage (Table 2)<\/h4>\n
13.3 Angle-Beam Probe Scanning Coverage (Table 3)<\/h4>\n
13.4 Discontinuity Classification<\/h4>\n
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14 Reporting Levels and Acceptance Criteria<\/h3>\n
Table 4 — Ferritic-Martensitic Steel Forgings<\/h4>\n
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\n \u53c2\u6570<\/th>\n Grade 1<\/th>\n Grade 2<\/th>\n Grade 3<\/th>\n Grade 4<\/th>\n<\/tr>\n \n Nominal Frequency (MHz)<\/td>\n ≥2<\/td>\n ≥2.5<\/td>\n ≥4<\/td>\n ≥5<\/td>\n<\/tr>\n \n Reporting Level (flat-bottom hole dia.)<\/td>\n >8 mm<\/td>\n >5 mm<\/td>\n >3 mm<\/td>\n >2 mm<\/td>\n<\/tr>\n \n Acceptance — Individual point discontinuity<\/td>\n <12 mm<\/td>\n <8 mm<\/td>\n <5 mm<\/td>\n <3 mm<\/td>\n<\/tr>\n \n Acceptance — Linear\/cluster discontinuities<\/td>\n <20 mm<\/td>\n <15 mm<\/td>\n <10 mm<\/td>\n <6 mm (≥DAC3\/3mm)<\/td>\n<\/tr>\n<\/table>\n Table 5 — Austenitic and Duplex Stainless Steel Forgings (Straight-Beam)<\/h4>\n
Table 6 — Austenitic and Duplex Stainless Steel Forgings (Angle-Beam DAC)<\/h4>\n
15 Sizing<\/h3>\n
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16 Report<\/h3>\n
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\nAppendices (Informational)<\/h3>\n
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\nDownload Original Standard (PDF)<\/h3>\n